Recently, portable user devices have provided more and more services and additional functions to users. A variety of applications are under development for execution in the portable user devices in order to increase the utilization of portable user devices and to satisfy various users' demands.
At least a few to hundreds of applications can be stored in a mobile, portable user device equipped with a touch screen, such as a smart phone, a portable phone, a laptop Personal Computer (PC), or a tablet PC, and a plurality of applications can be displayed on the touch screen of the portable user device. The portable user device and the applications associated therewith can be controlled by a touch or hovering of an input unit such as a finger, an electronic pen, a stylus pen, and/or the like.
If current flows through a coil of a digitizer, energy is transferred to an input unit having an electromagnetic resonant circuit. When current is blocked from the coil, a sensor of the digitizer measures the remaining resonation-induced voltage of the resonant circuit of the input unit and detects the input unit based on the measurement result. The portable user device and an application may be controlled according to the detecting result. Input units can be classified into a passive type and a digital type according to the method or mechanism by which the portable user device detects the input units.
A passive input unit includes passive devices such as an inductor (L), a Capacitor (C), and a Resistor (R). The passive input unit is generally configured to include only passive devices and operates with low power. Because the passive input unit does not require a battery, the passive unit is cost-effective, made small, and semi-permanent. However, the resonant frequency of the passive input unit may be changed due to a nearby magnetic material or conductive material that affects the resonant frequency, thereby imposing limitations on measuring pressure. In contrast, a digital input unit may include an Integrated Circuit (IC). Because the digital input unit measures a pressure and provides a digital pressure measurement to the digitizer, the digital input unit may not be sensitive to an external resonant frequency (e.g., the digital input unit may not be as sensitive to an external resonant frequency as a passive input unit). Further, the digital input unit may store input information (e.g., a pressure, a button input, erasure, and/or the like) applied by the input unit. However, the digital input unit requires power to drive the IC. Although the portable user device may supply power to the digital input device, the digital input device consumes much power, relative to the passive input device. If an additional power source is installed in the digital input device, the cost and size of the digital input device are increased. The digital input unit may conduct data communication usually in more slots than the passive input unit, thereby increasing the power consumption of the portable user device. An input unit may be implemented using various technologies, including, ElectroMagnetic Resonance (EMR), ultrasonic wave detection, optical detection, surface acoustic wave detection, and/or the like. Among the above identified technologies for implementing the input unit, the EMR scheme is widely used. In the EMR scheme, a substrate including a plurality of coils is used in a digitizer. When the input unit moves on or above the substrate, an electromagnetic field is changed. The changed electromagnetic field induces a signal to a coil and the digitizer detects the position of the input unit based on the induced signal.
The passive input unit and the digital input unit have various respective advantages and disadvantages. Although the digital input unit can provide an accurate pen pressure and can provide various use experiences through IC control, the digital input unit consumes much power, relative to the passive input unit. As a result, the digital input unit should require an additional power source or receive more power from a portable user device. In contrast, the passive input unit can operate even with a relatively low power received from a portable user device, without the need for using an additional power source. However, the passive input unit has limitations associated with transferring accurate information through a digital IC or providing a variety of use experiences.
Accordingly, there exists a need for increasing energy efficiency and user convenience by providing a method for switching the mode of a digitizer so as to take the advantages of various input units.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.